This invention is in the field of sewing machines; more particularly, it is concerned with a simplified method for implementing bobbin winding in place in a looptaker of a family sewing machine.
In the prior art, there are many examples of lock stitch sewing machine looptakers having the capability to replenish bobbin thread while the bobbin remains in place in the looptaker. An example of this prior art is found in the U.S. Pat. No. 3,693,566, issued on Sept. 26, 1972 to Ketterer.
In a prior art family lock stitch sewing machine using the capability disclosed in the above referred to patent, several steps were required to initiate the bobbin winding process. After the need for lower thread was perceived, the first step required in this electronically controlled prior art sewing machine, was firstly, to raise the presser foot so as to release the tension from the tension discs to allow thread to run freely from the upper large thread supply through the needle eye to the lower thread bobbin. Secondly, it was required to open the bed slide plate of the sewing machine to expose the bobbin winding mechanism therein and to actuate the bobbin winding latch to the winding position. Thirdly, a blind stitch pattern was selected in which several stitches are skipped and a small number of stitches are made in a continuous sequence. In this way, a stitch sequence could be provided in which an upper thread was brought down to the sewing machine looptaker in order to load an upper thread on the bobbin as is taught in the above referenced patent. Fourth, a single pattern repeat symbol must also be selected which will provide that only a single blind stitch sequence would be implemented so that a repeat up and down motion of the needle which might impede a smooth flow of thread from the spool to the bobbin, could be avoided. Fifthly, a thread ending from the sewing needle eye must be drawn beneath the elevated presser foot and wrapped around the thumb retaining screw for the presser foot, in order to provide a sufficient tautness to the trailing thread for a loop to be thrown that might be picked up by the looptaker.
It would be advantageous to simplify the above process insofar as possible. Many of the above steps, however, are not readily eliminated since the thread tension must be released, a bobbin winding mechanism must be armed and, steps must be taken to insure that a thread loop is provided for the looptaker. Further, in a sewing machine not having a single pattern repeat capability, some other means must be found for limiting the up and down motion of the needle which might interfere with the smooth flow of thread to the bobbin.
What is required is a method for implementing bobbin winding which might be implemented in a sewing machine not having pattern repeat capability without sacrificing any of the above noted requirements.